New crust is continually being pushed away from divergent boundaries (where sea-floor spreading occurs), increasing Earth's surface. But the Earth isn't getting any bigger. What happens, then, to ...

The Cascadia subduction zone, where the oceanic Juan de Fuca plate descends beneath the overlying North American plate, extends 1100 km from northern California to northern Vancouver Island.

The Hikurangi subduction zone is gradually expanding southwestward at the expense of the strike-slip and collisional boundary along the Southern Alps.

New crust is continually being pushed away from divergent boundaries (where sea-floor spreading occurs), increasing Earth's surface. But the Earth isn't getting any bigger. What happens, then, to ...